Shell and tube isolation in heat exchanger

ABSTRACT

A heat exchanger includes a heat exchanger shell formed from a first metal material, and a plurality of heat exchanger tubes extending through a plurality of tube openings in the heat exchanger shell. The plurality of heat exchanger tubes are formed from a second metal material different from the first metal material. A galvanic isolator is located at each tube opening of the plurality of tube openings, radially between the tube opening and the corresponding heat exchanger tube of the plurality of heat exchanger tubes. The galvanic isolator is configured to mitigate a galvanic reaction between the heat exchanger shell and the plurality of heat exchanger tubes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/354,388 filed Jun. 22, 2022, the disclosure of which is incorporatedby reference in its entirety.

BACKGROUND

Exemplary embodiments pertain to the art of heat exchangers, and morespecifically to corrosion mitigation for water cooled chillers.

In a water-cooled chiller, a flow of refrigerant is directed through oneor more shell and tube heat exchangers, such as an evaporator and acondenser, via a plurality of heat exchanger tubes. The heat exchangertubes are exposed to water inside the heat exchanger, which is used as aheat transfer fluid.

These heat exchanger tubes are suspended within the shell of thechiller, passing through steel end plates. An issue with galvaniccorrosion may arise when the heat exchanger tubes are formed fromaluminum. The steel construction is advantageous for medium to largechillers because of its strength given the size of the units. The use ofaluminum heat exchanger tubes allows for more technical and intricateshapes and features of the tubes. The steel to aluminum galvanic pair,if not mitigated, is very strong and highly detrimental to the aluminumheat exchanger tubes.

BRIEF DESCRIPTION

In one embodiment, a heat exchanger includes a heat exchanger shellformed from a first metal material, and a plurality of heat exchangertubes extending through a plurality of tube openings in the heatexchanger shell. The plurality of heat exchanger tubes are formed from asecond metal material different from the first metal material. Agalvanic isolator is located at each tube opening of the plurality oftube openings, radially between the tube opening and the correspondingheat exchanger tube of the plurality of heat exchanger tubes. Thegalvanic isolator is configured to mitigate a galvanic reaction betweenthe heat exchanger shell and the plurality of heat exchanger tubes.

Additionally or alternatively, in this or other embodiments the heatexchanger shell is formed from steel, and the plurality of heatexchanger tubes are formed from aluminum.

Additionally or alternatively, in this or other embodiments the galvanicisolator is formed from a non-metallic material.

Additionally or alternatively, in this or other embodiments the galvanicisolator is sleeve installed to one of the plurality of tube openings orthe plurality of heat exchanger tubes prior to installation of theplurality of heat exchanger tubes into the plurality of tube openings.

Additionally or alternatively, in this or other embodiments the galvanicisolator is a coating applied to one of the plurality of tube openingsor the plurality of heat exchanger tubes prior to installation of theplurality of heat exchanger tubes into the plurality of tube openings.

Additionally or alternatively, in this or other embodiments the coatingis a polytetrafluoroethylene (PTFE) material.

Additionally or alternatively, in this or other embodiments the galvanicisolator has a thickness in a range of 0.0005 inches to 0.001 inches.

Additionally or alternatively, in this or other embodiments installationof the plurality of heat exchanger tubes into the plurality of tubeopenings seals the plurality of tube openings.

In another embodiment, a chiller system includes a refrigerant circuithaving a flow of refrigerant circulating therethrough, and a fluidcircuit having a flow of heat transfer fluid circulating therethrough.The fluid circuit is operably connected to the refrigerant circuit at aheat exchanger assembly to transfer thermal energy between the flow ofrefrigerant and the fluid circuit. The heat exchanger assembly includesa heat exchanger shell formed from a first metal material, and aplurality of heat exchanger tubes extending through a plurality of tubeopenings in the heat exchanger shell. The plurality of heat exchangertubes are formed from a second metal material different from the firstmetal material. A galvanic isolator is located at each tube opening ofthe plurality of tube openings, radially between the tube opening andthe corresponding evaporator tube of the plurality of heat exchangertubes. The galvanic isolator is configured to mitigate a galvanicreaction between the heat exchanger shell and the plurality of heatexchanger tubes.

Additionally or alternatively, in this or other embodiments the heatexchanger shell is formed from steel, and the plurality of heatexchanger tubes are formed from aluminum.

Additionally or alternatively, in this or other embodiments the galvanicisolator is formed from a non-metallic material.

Additionally or alternatively, in this or other embodiments the galvanicisolator is sleeve installed to one of the plurality of tube openings orthe plurality of heat exchanger tubes prior to installation of theplurality of heat exchanger tubes into the plurality of tube openings.

Additionally or alternatively, in this or other embodiments the galvanicisolator is a coating applied to one of the plurality of tube openingsor the plurality of heat exchanger tubes prior to installation of theplurality of heat exchanger tubes into the plurality of tube openings.

Additionally or alternatively, in this or other embodiments the coatingis a polytetrafluoroethylene (PTFE) material.

Additionally or alternatively, in this or other embodiments the galvanicisolator has a thickness in a range of 0.0005 to 0.001 inches.

Additionally or alternatively, in this or other embodiments installationof the plurality of heat exchanger tubes into the plurality of tubeopenings seals the plurality of tube openings.

Additionally or alternatively, in this or other embodiments the heattransfer fluid is water.

In yet another embodiment, a method of assembling a heat exchangerincludes defining a heat exchanger shell formed from a first metalmaterial, the heat exchanger shell having a plurality of tube openingsformed therein, and providing a plurality of heat exchanger tubes formedfrom a second metal material different from the first metal material. Anon-metallic galvanic isolator is installed to one of an opening wall ofthe plurality of tube openings or the plurality of heat exchanger tubes.The plurality of heat exchanger tubes are installed into the pluralityof tube openings, such that the galvanic isolator is located radiallybetween the heat exchanger tube and the opening wall.

Additionally or alternatively, in this or other embodiments the galvanicisolator is a polymeric sleeve.

Additionally or alternatively, in this or other embodiments the galvanicisolator is a coating applied to one of the opening wall or the heatexchanger tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 is a schematic illustration of a chiller in accordance withexemplary embodiments;

FIG. 2 is a cross-sectional view of a heat exchanger in accordance withexemplary embodiments;

FIG. 3 is an illustration of an end sheet of heat exchanger shell inaccordance with exemplary embodiments;

FIG. 4 illustrates a galvanic isolator for a heat exchanger inaccordance with exemplary embodiments; and

FIG. 5 illustrates another galvanic isolator for a heat exchanger inaccordance with exemplary embodiments.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

Illustrated in FIG. 1 is an embodiment of a heating, ventilation and airconditioning (HVAC) system, for example a chiller 10. The chiller 10includes a refrigerant circuit 12, having a flow of refrigerant 14circulating therethrough. A compressor 16, a condenser 18, an expansiondevice 20, and an evaporator 22 arranged in series, with the flow ofrefrigerant 14 flowing through the components in sequence. The chiller10 further includes a fluid circuit 24 operably connected to therefrigerant circuit 12 at the evaporator 22. The fluid circuit 24 has aflow of heat transfer fluid, such as a flow of water 26 circulatingtherethrough. The flow of water 26 circulates between the evaporator 22and a heat exchanger, for example, a fan coil 28. The flow of water 26is cooled at the evaporator 22 via an exchange of thermal energy withthe flow of refrigerant 14. The cooled flow of water 26 is circulated tothe fan coil 28 where it absorbs thermal energy from a flow or air 30 toprovide cooling to a conditioned space 32. In some embodiments, a fan 34aids the exchange of thermal energy at the fan coil 28. Additionally, insome embodiments, the condenser 18 is water cooled, and utilizes acondenser flow of water 60 to reject thermal energy from the flow ofrefrigerant 14 to condense the flow of refrigerant 14.

Referring now to FIG. 2 , a cross-sectional view of a heat exchanger,such as the evaporator 22 or the condenser 18 of the chiller 10. Theheat exchanger includes a heat exchanger shell 36 that contains aplurality of heat exchanger tubes 38 through which the flow ofrefrigerant 14 is directed through the heat exchanger. In someembodiments, the heat exchanger tubes 38 are formed from an aluminummaterial. The flow of water 26 enters the heat exchanger via a waterinlet 40 and exits the heat exchanger after being either heated in thecase of the condenser 18, or cooled in the case of the evaporator 22,via the flow of refrigerant 14 at a water outlet 42. In someembodiments, such as illustrated in FIG. 2 , the flow of water 26 flowsover the heat exchanger 38 via gravity. In other embodiments, the heatexchanger is flooded, in which the heat exchanger shell 36 issubstantially filled with the flow of water 26.

Illustrated in FIG. 3 is an embodiment of an end sheet 44 of the heatexchanger shell 36. The end sheet 44 is formed from steel and includes aplurality of tube openings 46 through which the heat exchanger tubes 38are installed. To prevent (or at least mitigate) a galvanic reactionbetween the end sheet 44 and the heat exchanger tubes 38 when the heatexchanger tubes 38 are exposed to the flow of water 26, a galvanicisolator 48 is disposed between the heat exchanger tube 38 and the endsheet 44 at the tube opening 46, as shown in FIG. 4 . In a firstembodiment, illustrated in FIG. 4 , the galvanic isolator 48 is a verythin non-compressible sleeve or insert that is installed into the tubeopening 46 prior to installation of the heat exchanger tube 38 into thetube opening 46. The heat exchanger tube 38 is then installed into thetube opening 46 such that the galvanic isolator 48 is radially betweenthe heat exchanger tube 38 and an opening wall 50 of the tube opening46. The fit between the evaporator tube 38 and the opening wall 50 is aclose fit such that the tube opening 46 is sealed. The sleeve may beformed from a non-compressible polymeric or non-metallic material, andin some embodiments has a thickness in the range of 0.0005″ to 0.001″.

Utilizing a thin galvanic isolator 48 allows for use of existing spacingof heat exchanger tubes 38 in the heat exchanger, without having tocompensate for the presence of the galvanic isolator 48, which mayaffect heat exchanger performance. While in the embodiment of FIG. 4 thegalvanic isolator 48 is installed into the tube opening 46, in otherembodiments the galvanic isolator 48 may be installed to the evaporatortube 38 prior to the heat exchanger tube 38 being into the tube opening46.

In another embodiment, illustrated in FIG. 5 , the galvanic isolator 48is a coating applied directly to the opening wall 50 of the tube opening46 prior to installation of the heat exchanger tube 38 into the tubeopening 46. In some embodiments the coating material is, for example,polytetrafluoroethylene (PTFE) material applied by, for example, a sprayor dip process. As with the sleeve, it is desired that the coating isthin, in the range of 0.0005″ to 0.001″ thickness, so that the spacingof the heat exchanger tubes 38 will not be affected by the use of thegalvanic isolator 48. One skilled in the art will readily appreciatethat the coating is not limited to PTFE material, and other thincoatings such as nano coatings or the like may be suitable. While in theembodiment of FIG. 5 , the coating is applied to the opening wall 50 ofthe tube opening 46, one skilled in the art will appreciate that thatcoating may be applied instead to the heat exchanger tube 38 prior toinstallation of the heat exchanger tube 38 into the tube opening 46.Further, in some embodiments the coating may be applied to both the heatexchanger tube 38 and the opening wall 50 prior to installation of theheat exchanger tube 28 into the tube opening 46.

Use of the galvanic isolator 48 prevents (or at least mitigates) thegalvanic pair from forming between the end sheet 44 and the heatexchanger tube 38, thus preventing (or at least mitigating) corrosion ofthe heat exchanger tube 38, which leads to an extension of the servicelife of the heat exchanger.

The term “about” is intended to include the degree of error associatedwith measurement of the particular quantity based upon the equipmentavailable at the time of filing the application.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,element components, and/or groups thereof.

While the present disclosure has been described with reference to anexemplary embodiment or embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe present disclosure. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this present disclosure, but that the present disclosurewill include all embodiments falling within the scope of the claims.

What is claimed is:
 1. A heat exchanger comprising: a heat exchanger shell formed from a first metal material; a plurality of heat exchanger tubes extending through a plurality of tube openings in the heat exchanger shell, the plurality of heat exchanger tubes formed from a second metal material different from the first metal material; and a galvanic isolator disposed at each tube opening of the plurality of tube openings, radially between the tube opening and the corresponding heat exchanger tube of the plurality of heat exchanger tubes, the galvanic isolator configured to mitigate a galvanic reaction between the heat exchanger shell and the plurality of heat exchanger tubes.
 2. The heat exchanger of claim 1, wherein: the heat exchanger shell is formed from steel; and the plurality of heat exchanger tubes are formed from aluminum.
 3. The heat exchanger of claim 1, wherein the galvanic isolator is formed from a non-metallic material.
 4. The heat exchanger of claim 1, wherein the galvanic isolator is sleeve installed to one of the plurality of tube openings or the plurality of heat exchanger tubes prior to installation of the plurality of heat exchanger tubes into the plurality of tube openings.
 5. The heat exchanger of claim 1, wherein the galvanic isolator is a coating applied to one of the plurality of tube openings or the plurality of heat exchanger tubes prior to installation of the plurality of heat exchanger tubes into the plurality of tube openings.
 6. The heat exchanger of claim 5, wherein the coating is a polytetrafluoroethylene (PTFE) material.
 7. The heat exchanger of claim 1, wherein the galvanic isolator has a thickness in a range of 0.0005 to 0.001 inches.
 8. The heat exchanger of claim 1, wherein installation of the plurality of heat exchanger tubes into the plurality of tube openings seals the plurality of tube openings.
 9. A chiller system comprising: a refrigerant circuit having a flow of refrigerant circulating therethrough; a fluid circuit having a flow of heat transfer fluid circulating therethrough, the fluid circuit operably connected to the refrigerant circuit at a heat exchanger assembly to transfer thermal energy between the flow of refrigerant and the fluid circuit, the heat exchanger assembly comprising: a heat exchanger shell formed from a first metal material; a plurality of heat exchanger tubes extending through a plurality of tube openings in the heat exchanger shell, the plurality of heat exchanger tubes formed from a second metal material different from the first metal material; and a galvanic isolator disposed at each tube opening of the plurality of tube openings, radially between the tube opening and the corresponding evaporator tube of the plurality of heat exchanger tubes, the galvanic isolator configured to mitigate a galvanic reaction between the heat exchanger shell and the plurality of heat exchanger tubes.
 10. The chiller system of claim 9, wherein: the heat exchanger shell is formed from steel; and the plurality of heat exchanger tubes are formed from aluminum.
 11. The chiller system of claim 9, wherein the galvanic isolator is formed from a non-metallic material.
 12. The chiller system of claim 9, wherein the galvanic isolator is sleeve installed to one of the plurality of tube openings or the plurality of heat exchanger tubes prior to installation of the plurality of heat exchanger tubes into the plurality of tube openings.
 13. The chiller system of claim 9, wherein the galvanic isolator is a coating applied to one of the plurality of tube openings or the plurality of heat exchanger tubes prior to installation of the plurality of heat exchanger tubes into the plurality of tube openings.
 14. The chiller system of claim 13, wherein the coating is a polytetrafluoroethylene (PTFE) material.
 15. The chiller system of claim 9, wherein the galvanic isolator has a thickness in a range of 0.0005 to 0.001 inches.
 16. The chiller system of claim 9, wherein installation of the plurality of heat exchanger tubes into the plurality of tube openings seals the plurality of tube openings.
 17. The chiller system of claim 9, wherein the heat transfer fluid is water.
 18. A method of assembling a heat exchanger comprising: defining a heat exchanger shell formed from a first metal material, the heat exchanger shell having a plurality of tube openings formed therein; providing a plurality of heat exchanger tubes formed from a second metal material different from the first metal material; installing a non-metallic galvanic isolator to one of an opening wall of the plurality of tube openings or the plurality of heat exchanger tubes; and installing the plurality of heat exchanger tubes into the plurality of tube openings, such that the galvanic isolator is disposed radially between the heat exchanger tube and the opening wall.
 19. The method of claim 18, wherein the galvanic isolator is a polymeric sleeve.
 20. The method of claim 18, wherein the galvanic isolator is a coating applied to one of the opening wall or the heat exchanger tube. 